They include sites that seem to be their competitors because they earn referral fees when you buy memberships. A couple mentioned in scam forums even try to dupe you into buying the same list at other membership sites they own under different names. Naturally, these sites also have an incentive to exaggerate how much you'll earn from online paid surveys.

All of the surveys from RAND Health Care are public documents, available without charge. Please provide an appropriate citation when using these products. In some cases, the materials themselves include specific instructions for citation. Some materials listed are not available from RAND Health Care. Those links will take you to other websites, where you will find instructions for use. There are no further permissions necessary.
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Swagbucks is the world’s largest free rewards community. Our members are helping shape the future of products that will be released all around the world. We have relationships with hundreds of brands, who give us thousands of new online surveys a week to provide to you. Your Swagbucks membership is completely free and you can join by filling out the simple registration form above. Once you are registered, you can start earning points by completing paid online surveys. And the best part is, you can take these paid surveys whenever you want and anywhere you want. Cell phone, Laptop, PC or Tablet.